QImage out of memory and OpenMP conflict

JulienMaille

Dear all,
I have a program that handles live image processing and display.
A few days ago, I started getting random error messages saying:
[quote]QImage: out of memory, returning null image[/quote]When checking the memory consumption, I saw nothing alarming, around 120M for my application and this number is stable over a few hours.

After hours chasing that bug, I finally narrowed it down to a part of the code that perform a flip of the image. If I comment out the openMP macro, it works fine. If I keep it, then I have random crashes after a couple of hours.
@if( softFlipX )
{
#pragma omp parallel for
for( int y=0; y<_imgH; ++y ) // _imgH,_imgW ~= 512
{
for( int x=0; x<_imgW/2; ++x )
{
int temp = buf[x+y*_imgW];
buf[x+y*_imgW]=buf[_imgW-1-x+y*_imgW];
buf[_imgW-1-x+y*_imgW]=temp;
}
}
}@
So I'm wondering: what can trigger the "out of memory" message, and how does it conflict with the part of the code that uses openMP?
Thanks a lot for your help!

EDIT:
the problem occurs in
@QImage QImage::convertToFormat(Format format, Qt::ImageConversionFlags flags) const
{
if (!d || d->format == format)
return *this;

if (format == Format_Invalid || d->format == Format_Invalid)
    return QImage();

const Image_Converter *converterPtr = &converter_map[d->format][format];
Image_Converter converter = *converterPtr;
if (converter) {
    QImage image(d->width, d->height, format);

--> QIMAGE_SANITYCHECK_MEMORY(image);@
d->width = d->height = 528
format = RGB32
and I have plenty of free memory.

SGaist

Hi,

This question is a bit low-level, you should bring it to the interest mailing list, you'll find Qt's developers/maintainers there (this forum is more user oriented)

JulienMaille

Finally found it:
http://connect.microsoft.com/VisualStudio/feedback/details/340292/openmp-leaks-thread-handels-and-memory-when-used-in-threads

SGaist

Interesting... Thanks for sharing !

JulienMaille

And the workaround for msvc:
@ omp_set_dynamic(1);@